Overview of Subcritical Extraction Equipment
Currently, the production of common edible oils, such as soybean oil, rapeseed oil, and sunflower oil, is mostly done through solvent extraction, using hexane or n-hexane, commonly known as solvent #6. Due to the high boiling point of this solvent, the removal of the solvent from crude oil and meal requires temperatures of 120°C, which damages heat-sensitive nutrients in the oil and meal.
This leads to significant denaturation of active ingredients such as proteins, flavonoids, alkaloids, and vitamins. Consequently, the value of the meal after oil extraction is limited, and most of it is used as feed and fertilizer, with no further development or utilization.
Principle of Subcritical Extraction Equipment
Subcritical Extraction Equipment is conducted under closed, oxygen-free conditions, making it simple, safe, and convenient to operate. The solvent used in subcritical extraction equipment is a gas at room temperature and pressure, but becomes a liquid when pressurized.
The basic principle of this process is that at room temperature and a certain pressure (0.3MPa-0.8MPa), a subcritical fluid countercurrent is used to extract oilseed germs or pellets (such as grape seeds, flax seeds, walnut kernels, wheat germ, peony seeds, pumpkin seeds, and evening primrose seeds).
The solvent in the mixed oil and meal is then decompressed and vaporized. The vaporized solvent gas is then compressed, condensed, and liquefied by a compressor for recycling. The heat required for solvent vaporization during the desolventizing process is partially absorbed by the system itself, while the remaining heat is supplied by the heating system.
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Subcritical extraction process:
1.
Open the feed valve and load the pretreated raw materials into the extraction tank. Close the feed valve and start the vacuum pump to exhaust the air in the extraction tank.
2.
Use the solvent pump to inject the subcritical fluid into the extraction tank to soak the raw materials and start the stirring extraction.
3.
Use the solvent pump to extract the mixed oil from the extraction tank and pump it into the evaporation tank.
4.
Open the compressor outlet valve, start the compressor, connect the extraction tank and the compressor intake to vaporize the solvent remaining in the meal. The solvent gas enters the compressor, is compressed, condensed and liquefied by the condenser, and then flows back to the solvent turnover tank for recycling.
5.
Connect the evaporation tank and the compressor intake to indirectly heat the evaporation tank so that the solvent evaporates and is separated from the crude oil.
6.
The solvent vapor is compressed, condensed and liquefied by the compressor, and then flows back to the solvent turnover tank for recycling. The crude oil is discharged from the evaporation tank.
7.
Operating process parameters: temperature 40℃, extraction pressure 0.4~0.7Mpa, extraction times 3~5 times (depending on the oil content of raw materials); mixed oil concentration 10~40%, temperature 40~45℃, mixed oil evaporation temperature 45~60℃, mixed oil desolventizing vacuum degree -0.095Mpa;
Advantages of subcritical extraction equipment?
The quality of the meal obtained after extraction is good, the rate of water-soluble protein in the meal is greater than 95%, the residual oil in the meal is less than 1%, and the residual solvent is less than 500ppm;
The solvent consumption is low, less than 6kg per ton of material;
No steam is required, only 90℃ hot water is sufficient, which can save 70% of heat energy compared to No. 6 solvent;
There is no "three wastes pollution" in production, which is an environmental protection project;
The extracted oil is light in color, low in lecithin content, and the residual solvent in the oil can be less than 1ppm;
The extraction is carried out at room temperature and the desolventizing is carried out at low temperature (less than 50℃), which has almost no damage to the heat-sensitive substances in the meal and oil.
Small investment and low production cost (compared to carbon dioxide equipment);
Subcritical fluid of the subcritical extraction equipment is widely available and low in price. This solvent is available in all oil and gas fields and refineries, and its price is lower than other extraction agents.
